dbcve.org
TomcatWeb server / proxy · Apache

CVE-2023-34981

HIGH · 7.5 CVSS v3.1 Published 2023-06-21
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A regression in the fix for bug 66512 in Apache Tomcat 11.0.0-M5, 10.1.8, 9.0.74 and 8.5.88 meant that, if a response did not include any HTTP headers no AJP SEND_HEADERS messare woudl be sent for the response which in turn meant that at least one AJP proxy (mod_proxy_ajp) would use the response headers from the previous request leading to an information leak.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A regression in Apache Tomcat's AJP connector causes an information leak when responses contain no HTTP headers. The AJP SEND_HEADERS message is not sent, causing mod_proxy_ajp to reuse response headers from previous requests, exposing sensitive data between users.

MitigationUpgrade to Apache Tomcat 8.5.89+, 9.0.75+, 10.1.9+, or 11.0.0-M6+ to obtain the fix, or ensure all responses include at least one HTTP header.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
TomcatWeb server / proxy
Affected:= 8.5.88= 9.0.74= 10.1.8= 11.0.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Tomcat installation directory
    Locate the Tomcat installation path (commonly /opt/tomcat, /usr/share/tomcat, or C:\Program Files\Apache\Tomcat on Windows). Check for the presence of the main Tomcat directories: bin, conf, lib, logs.
    Affected if N/A - this is the prerequisite to perform subsequent checks
  2. Determine installed Tomcat version
    Read the RELEASE-NOTES file in the Tomcat home directory, or check the version property in the bin/version.sh (Linux) or bin\version.bat (Windows) script. Alternatively, examine the manifest in the catalina.jar file located in the lib directory.
    Affected if The installed version matches 8.5.88, 9.0.74, 10.1.8, or 11.0.0 exactly
  3. Verify AJP connector is enabled
    Examine the conf/server.xml configuration file and look for an AJP connector definition, typically with protocol="AJP/1.3" and port="8009" (or similar AJP port).
    Affected if An active AJP connector is defined and uncommented in server.xml, enabling AJP communication with a frontend web server
  4. Confirm AJP connector is in use
    Check if the AJP connector is bound to a listening port (default 8009) and actively processing requests, or review proxy configuration on the frontend web server (e.g., mod_proxy_ajp in Apache HTTP Server) to confirm AJP forwarding is configured.
    Affected if The AJP connector is listening and receiving forwarded requests from a reverse proxy via the AJP protocol
  5. Identify if responses may lack HTTP headers
    Review the application deployed on Tomcat to determine if any servlet, JSP, or other endpoint can return responses without setting at least one HTTP response header. Check for scenarios where response.setHeader, response.addHeader, or equivalent methods are not called.
    Affected if Any deployed application can produce responses (such as error pages, API responses, or static content) that contain zero HTTP headers

You are affected if your Tomcat version is exactly 8.5.88, 9.0.74, 10.1.8, or 11.0.0 AND the AJP connector is enabled and in use AND your applications can return responses without any HTTP headers, potentially leaking headers from previous requests to other users.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Apache Tomcat 8.5.89+, 9.0.75+, 10.1.9+, or 11.0.0-M6+ to obtain the fix, or ensure all responses include at least one HTTP header.

Recommended fix High confidence

Tomcat 8.5.89 (for 8.5.x); Tomcat 9.0.75 (for 9.0.x); Tomcat 10.1.9 (for 10.1.x); Tomcat 11.0.1 (for 11.0.x)

  1. 1. Identify the currently running Apache Tomcat version using the version.sh script or server info page
  2. 2. Determine which Tomcat branch you are using (8.5.x, 9.0.x, 10.1.x, or 11.0.x)
  3. 3. Download the appropriate fixed Tomcat release for your branch from the official Apache Tomcat download page (tomcat.apache.org)
  4. 4. Stop the Tomcat service or instance
  5. 5. Back up your existing Tomcat installation including conf/ directory with all configuration files
  6. 6. Extract the new fixed version to your Tomcat installation directory
  7. 7. Restore your custom configuration files from the backup (server.xml, context.xml, etc.)
  8. 8. Restore any deployed web applications from the backup
Caveat Minor point release upgrades typically have no breaking changes; however, always review the Tomcat migration guide and release notes for any configuration or API behavior differences before upgrading production systems

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Tomcat Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-34981 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data